Motor graders are used primarily as a finishing tool to sculpt a surface of a construction site to a final shape and contour. Typically, motor graders include many hand-operated controls to steer the wheels of the grader, position a blade, and articulate the front frame of the grader. The blade is adjustably mounted to the front frame to move relatively small quantities of earth from side to side. The articulation angle is adjusted by rotating the front frame of the grader relative to the rear frame of the grader.
While preparing the subsurface of, for example, a parking lot, highway, or golf course, it is desirable to ensure the accuracy of the boundary and contour of the work area. A motor grader may make multiple passes back and forth across the work area in order to completely cover an entire region within the boundary. Each of these passes may involve check points spaced out at regular intervals that define a straight path with a 180 degree turn at the end thereof. Furthermore, each pass is offset by a certain amount from the previous pass. To produce a variety of surface geometries at a construction site, the blade and the frame may be adjusted by an operator to many different positions. Positioning the blade of a motor grader is a complex and time-consuming task and is difficult to do when making complicated cuts or contouring surfaces, and to do so while also steering the grader.
Because grading tasks are complicated and time-consuming, it is difficult for the operator to simultaneously accomplish all of the tasks necessary for finely grading a complex work site. The operator must control machine trajectory, the complexity of which may increase with increasing numbers of passes and turns. Furthermore, the operator must control surface elevations, angles, and cut depths. The difficulty of such operations may reduce the productivity and efficiency of the operator.
One way to simplify operator control and allow focusing on the sculpting performed by the blade is to autonomously steer the machine. One example is U.S. Pat. No. 6,907,336 issued to Gray et al. (Gray) on Jun. 14, 2005. Gray discloses a machine that generates a travel path and then uses a navigation system to follow the generated path. The system in the Gray patent has a vehicular guidance system and a path planner. The path planner includes a creator, which creates a machine travel row transparency based on user input and places it over a mapped area. The mapped area represents the work area of the vehicle, and the travel rows represent the path over which the machine will travel while grading the work area. The path planner also includes a splitter, which splits the travel rows into sections defined by the intersections of travel rows and the boundary of the work area. Nodes are created at the section boundaries signifying the beginning or termination of work along each travel path. A data processor identifies and locates each node and determines the most efficient path by interconnecting the nodes in a continuously looping line. Once the path is created and the coordinates of the path are determined, the system uses the navigation system to steer the vehicle through the generated path.
Although the system in the Gray patent generates a path along which the motor grader is automatically driven, the path is based on a pre-made map of the work site. Because the Grey system relies on pre-made maps, the number and variety of work sites open to automatic steering may be limited by the inventory of maps. In addition, the storage of such pre-made maps can require additional memory, adding to the cost of the system.
Additionally, the system in the Gray patent offers only one possible path based on the least number of passes required to traverse the work site. Although this one path may be the optimal path for some work sites, it may provide a sub-optimal path for others. For example, the most optimal path for a particular work site may be based on the starting point of the path rather than the number of passes traversing the work site. If the path is designed based on the minimal number of passes, it might be suboptimal because it may originate at an undesired point. Furthermore, it might be impossible to fully sculpt the work site along a particular path because of obstructions omitted from the stored map.
Furthermore, the system in Gray fails to ensure that the motor grader is placed within the vicinity of the initial position and orientation suggested by the path. Without an automatic mechanism for initially positioning the motor grader, the grading process may begin with the motor grader misaligned. Any deviation from the path caused by the misalignment may cause errors in the grading. Such generated errors may require corresponding corrections leading to decreased efficiency and increased construction costs.
The disclosed automated steering system is directed to overcoming one or more of the problems set forth above.